Pressure sensitive adhesive tapes are used for a variety of applications from household tapes that are dispensed from a disposable hand held dispenser to carton sealing tapes that are used at a very high volume and are applied rapidly by semiautomatic and automatic taping heads. One of the problems encountered in automatic taping, especially when the tape has a relatively stiff adhesive, is that unwinding the tape from the roll rapidly results in an unacceptably high level of noise which causes discomfort and potential hearing damage to the workers in the taping area. One solution is to supply ear plugs to the workers but the plugs are inconvenient to use and may not always be used.
Solutions to the problem, wherein the product construction is changed, have been suggested by others. U.S. Pat. No. 4,699,816 describes the addition of mineral oil or a synthetic alkylbenzene oil to the adhesive, as well as modifying the backing and the treatment on the backside of the tape. The patent recognizes that there is a noise problem with polyolefin backings, and that a polypropylene backing is particularly noisy when unwound rapidly.
Also, tapes have been made having a pressure sensitive adhesive made with a slight amount of an organic solvent so that the softer adhesive will release from the backsize at a lower noise level. This solution is not desirable because of the use of organic solvents.
In both of the above mentioned cases, the adhesive properties can be undesirably affected. Tapes having softer pressure sensitive adhesives tend to unwind with lower noise levels, but the shear strength of the adhesive is generally lower. Softer adhesives can also exhibit cohesive failure as the tape is unwound, leaving adhesive residue on the backside of the tape.
Tapes with polyvinylchloride (PVC) backings are available which have a low noise unwind. However, the unwind force is generally very high and the tapes cannot be unwound rapidly.
Italian Patent Application No. 21842/A2 describes a method to increase the critical surface tension of the backside of a pressure sensitive adhesive coated tape to a level higher than 33 dynes/cm to reduce the noise level.
Italian Patent Application No. 8223156 (Galli), filed Sep. 2, 1982, describes the modification of release coatings through inclusion of a fluorinated compound, a reactive silicone compound, a silicone compound modified with a polyamidic resin, a halogenated polyolefinic resin, or other compound or resin.
Release coatings are known and a number of them are commercially available. Silicone release coatings typically have a very low unwind force, and generally have a low noise at unwind with most types of pressure sensitive adhesives. However, in a roll of tape, the low unwind force can also cause the pressure sensitive adhesive to release or slide from the backside of the underlying lap causing the roll of tape to telescope. It is also difficult to provide a controlled unwind force with silicone coatings.
EP 464706 describes an ultraviolet-curable silicone composition having an epoxy-functional polyorganosiloxane and a copolymer for regulating peel strength that is soluble in the polyorganosiloxane. The copolymer is selected from MQ, MT, or MDQ copolymers.
Epoxypolysiloxanes have been found to provide useful release compositions as described in, for example, U.S. Pat. Nos. 4,279,719, 4,313,988 and 4,822,687. However, there is no teaching that any of the compositions provide a low noise unwind pressure sensitive adhesive tape having a controlled unwind force.
It would therefore be desirable to have a release composition for pressure sensitive adhesive tapes which could be modified to provide the desired unwind force for a given adhesive, but would unwind readily without excessive noise levels.